Embodiments of the disclosure relate generally to systems and methods of unified common mode voltage injection to achieve multiple functions.
Power converters, particularly multi-level power converters, are increasingly used for performing power conversion in a wide range of applications due to the advantages of high power quality waveform and high voltage capability. For example, multi-level power converters may be used for performing DC-to-AC power conversion to supply single-phase or multi-phase AC voltages to electric motors in vehicles and/or pumps. Multi-level converters may also be used in power generation systems such as wind turbine generators and solar generators for performing DC-to-AC power conversion to supply single-phase or multi-phase AC voltages for power grid transmission and distribution.
Typically, the power converters are designed to regulate or control various characteristic parameters in association with the operation of the power converters to meet certain requirements and/or ensure reliable operations. For example, the output AC voltage and/or current provided from the power converters may be controlled to have a low total harmonic distortion (THD) since high-order harmonic signals may degrade the quality of power delivered to the power grid or may cause damage to the electric motors. In addition, a DC link consisting of at least two DC capacitors is controlled to minimize the voltage difference between the two DC capacitors to avoid stressing the switching devices and/or creation of undesired harmonic signals. However, to achieve the purposes of controlling the various characteristic parameters, the conventional system typically employs different control strategies, such as carrier phase-shifting for reducing the output THD and space-vector switching state selection for balancing the DC voltages at the DC link.